RFC 9545

Path Segment Identifier in MPLS-Based Segment Routing Networks, February 2024

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W. Cheng, Ed.
H. Li
C. Li, Ed.
R. Gandhi
R. Zigler
spring (rtg)

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DOI:  https://doi.org/10.17487/RFC9545

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A Segment Routing (SR) path is identified by an SR segment list. A subset of segments from the segment list cannot be leveraged to distinguish one SR path from another as they may be partially congruent. SR path identification is a prerequisite for various use cases such as performance measurement and end-to-end 1+1 path protection.

In an SR over MPLS (SR-MPLS) data plane, an egress node cannot determine on which SR path a packet traversed the network from the label stack because the segment identifiers are removed from the label stack as the packet transits the network.

This document defines a Path Segment Identifier (PSID) to identify an SR path on the egress node of the path.

For the definition of Status, see RFC 2026.

For the definition of Stream, see RFC 8729.

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